AWS LambdaでAWS CLIから関数にLayerを追加・削除する方法

AWS CLIからLambda関数にLayerを追加・削除する方法がわかりにくかったのでメモ。


## 前提

- AWSアカウントがある
- AWS CLIが利用可能
- 検証できるLambda関数がある
  - なければ新規作成


## Lambda Layerを作成

検証で利用するLayerを作成します。今回は関数内で参照しないので、ファイル内に`//` だけ含んだファイルでLayerを作成します。空ファイルだとだめでした。
AWS CLIだと`aws lambda publish-layer-version` コマンドで作成ができます。

```console
> echo '//' layer.js

> zip layer.zip layer.js

> aws lambda publish-layer-version \
  --layer-name test-layer-1 \
  --zip-file fileb://layer.zip \
  --compatible-runtimes nodejs8.10

{
    "Content": {
        "Location": "https://prod-04-2014-layers.s3.amazonaws.com/snapshots/(略)",
        "CodeSha256": "T4pRG6jK1iy8rjqOxxP2t3R1YSb5hl61Q90xHYHkePE=",
        "CodeSize": 168
    },
    "LayerArn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-1",
    "LayerVersionArn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-1:1",
    "Description": "",
    "CreatedDate": "2019-06-20T07:05:45.061+0000",
    "Version": 1,
    "CompatibleRuntimes": [
        "nodejs8.10"
    ]
}


> aws lambda publish-layer-version \
  --layer-name test-layer-2 \
  --zip-file fileb://layer.zip \
  --compatible-runtimes nodejs8.10

{
    "Content": {
        "Location": "https://prod-04-2014-layers.s3.amazonaws.com/snapshots/(略)",
        "CodeSha256": "T4pRG6jK1iy8rjqOxxP2t3R1YSb5hl61Q90xHYHkePE=",
        "CodeSize": 168
    },
    "LayerArn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-2",
    "LayerVersionArn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-2:1",
    "Description": "",
    "CreatedDate": "2019-06-20T07:07:28.453+0000",
    "Version": 1,
    "CompatibleRuntimes": [
        "nodejs8.10"
    ]
}
```


## Lambda Layerを関数に追加

検証用の関数`use-lambda-layer` がある前提です。

Layerを指定する場合、上記にあるARNのうち、バージョンまで含まれている`LayerVersionArn` を指定する必要があります。複数Layerを追加するにはスペース区切りで指定します。

```console
# 1つ追加
> aws lambda update-function-configuration \
  --function-name use-lambda-layer \
  --layers \
    "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-1:1"

{
    "FunctionName": "use-lambda-layer",
    "FunctionArn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:function:use-lambda-layer",
    "Runtime": "nodejs8.10",
    "Role": "arn:aws:iam::xxxxxxxxxxxx:role/service-role/xxxxxxxxxxxx",
    "Handler": "index.handler",
    "CodeSize": 262,
    "Description": "",
    "Timeout": 3,
    "MemorySize": 128,
    "LastModified": "2019-06-20T07:11:20.502+0000",
    "CodeSha256": "F8AUyhyiHz5dsBaSl6+u86B5oiwWD3jtdi3IuvB0eKE=",
    "Version": "$LATEST",
    "VpcConfig": {
        "SubnetIds": [],
        "SecurityGroupIds": [],
        "VpcId": ""
    },
    "TracingConfig": {
        "Mode": "PassThrough"
    },
    "RevisionId": "f8ad4fd8-b8d2-4aba-ba12-9f28759df79d",
    "Layers": [
        {
            "Arn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-1:1",
            "CodeSize": 168
        }
    ]
}


# 2つ追加
> aws lambda update-function-configuration \
  --function-name use-lambda-layer \
  --layers \
    "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-1:1" \
    "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-2:1"

{
    "FunctionName": "use-lambda-layer",
    "FunctionArn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:function:use-lambda-layer",
    "Runtime": "nodejs8.10",
    "Role": "arn:aws:iam::xxxxxxxxxxxx:role/service-role/xxxxxxxxxxxx",
    "Handler": "index.handler",
    "CodeSize": 262,
    "Description": "",
    "Timeout": 3,
    "MemorySize": 128,
    "LastModified": "2019-06-20T07:12:47.938+0000",
    "CodeSha256": "F8AUyhyiHz5dsBaSl6+u86B5oiwWD3jtdi3IuvB0eKE=",
    "Version": "$LATEST",
    "VpcConfig": {
        "SubnetIds": [],
        "SecurityGroupIds": [],
        "VpcId": ""
    },
    "TracingConfig": {
        "Mode": "PassThrough"
    },
    "RevisionId": "8737bdfe-3b0d-404e-b3a0-c9fd57e971a9",
    "Layers": [
        {
            "Arn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-1:1",
            "CodeSize": 168
        },
        {
            "Arn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-2:1",
            "CodeSize": 168
        }
    ]
}
```


## Lambda Layerを関数から削除

Layerを削除というよりは利用するLayerを再指定することになります。
すべて削除するには`--layers []` として、`空配列`を指定する必要があります。~~わかりにくい~~

```console
# 1つ削除
> aws lambda update-function-configuration \
  --function-name use-lambda-layer \
  --layers \
    "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-2:1"

{
    "FunctionName": "use-lambda-layer",
    "FunctionArn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:function:use-lambda-layer",
    "Runtime": "nodejs8.10",
    "Role": "arn:aws:iam::xxxxxxxxxxxx:role/service-role/xxxxxxxxxxxx",
    "Handler": "index.handler",
    "CodeSize": 262,
    "Description": "",
    "Timeout": 3,
    "MemorySize": 128,
    "LastModified": "2019-06-20T07:13:27.749+0000",
    "CodeSha256": "F8AUyhyiHz5dsBaSl6+u86B5oiwWD3jtdi3IuvB0eKE=",
    "Version": "$LATEST",
    "VpcConfig": {
        "SubnetIds": [],
        "SecurityGroupIds": [],
        "VpcId": ""
    },
    "TracingConfig": {
        "Mode": "PassThrough"
    },
    "RevisionId": "fa942867-332a-4d32-ae2d-31209ce9cc30",
    "Layers": [
        {
            "Arn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:layer:test-layer-2:1",
            "CodeSize": 168
        }
    ]
}


# 全部削除
> aws lambda update-function-configuration \
  --function-name use-lambda-layer \
  --layers []

{
    "FunctionName": "use-lambda-layer",
    "FunctionArn": "arn:aws:lambda:us-east-1:xxxxxxxxxxxx:function:use-lambda-layer",
    "Runtime": "nodejs8.10",
    "Role": "arn:aws:iam::xxxxxxxxxxxx:role/service-role/xxxxxxxxxxxx",
    "Handler": "index.handler",
    "CodeSize": 262,
    "Description": "",
    "Timeout": 3,
    "MemorySize": 128,
    "LastModified": "2019-06-20T07:13:53.065+0000",
    "CodeSha256": "F8AUyhyiHz5dsBaSl6+u86B5oiwWD3jtdi3IuvB0eKE=",
    "Version": "$LATEST",
    "VpcConfig": {
        "SubnetIds": [],
        "SecurityGroupIds": [],
        "VpcId": ""
    },
    "TracingConfig": {
        "Mode": "PassThrough"
    },
    "RevisionId": "c060cba7-2cf4-48af-88d3-4e5f653965a2"
}
```


## 参考

AWS Lambda Layers - AWS Lambda
https://docs.aws.amazon.com/lambda/latest/dg/configuration-layers.html

publish-layer-version — AWS CLI 1.16.182 Command Reference
https://docs.aws.amazon.com/cli/latest/reference/lambda/publish-layer-version.html